Potential of conserved antigenic sites in development of universal SARS-like coronavirus vaccines.

Given pandemic risks of zoonotic SARS-CoV-2 variants and other SARS-like coronaviruses in the future, it is valuable to perform studies on conserved antigenic sites to design universal SARS-like coronavirus vaccines. By using antibodies obtained from convalescent COVID-19 patients, we succeeded in functional comparison of conserved antigenic sites at multiple aspects with each other, and even with SARS-CoV-2 unique antigenic sites, which promotes the cognition of process of humoral immune response to the conserved antigenic sites. The conserved antigenic sites between SARS-CoV-2 and SARS-CoV can effectively induce affinity maturation of cross-binding antibodies, finally resulting in broadly neutralizing antibodies against multiple variants of concern, which provides an important basis for universal vaccine design, however they are subdominant, putatively due to their lower accessibility relative to SARS-CoV-2 unique antigenic sites. Furthermore, we preliminarily design RBDs to improve the immunogenicity of these conserved antigenic sites. Our study focusing on conserved antigenic sites provides insights for promoting the development of universal SARS-like coronavirus vaccines, thereby enhancing our pandemic preparedness.

Stability of SARS-CoV-2 on inanimate surfaces: A review.

The stability of SARS-CoV-2 for varying periods on a wide range of inanimate surfaces has raised concerns about surface transmission; however, there is still no evidence to confirm this route. In the present review, three variables affecting virus stability, namely temperature, relative humidity (RH), and initial virus titer, were considered from different experimental studies. The stability of SARS-CoV-2 on the surfaces of six different contact materials, namely plastic, metal, glass, protective equipment, paper, and fabric, and the factors affecting half-life period was systematically reviewed. The results showed that the half-life of SARS-CoV-2 on different contact materials was generally 2-10 h, up to 5 d, and as short as 30 min at 22 °C, whereas the half-life of SARS-CoV-2 on non-porous surfaces was generally 5-9 h d, up to 3 d, and as short as 4 min at 22 â„ƒ. The half-life on porous surfaces was generally 1-5 h, up to 2 d, and as short as 13 min at 22 °C. Therefore, the half-life period of SARS-CoV-2 on non-porous surfaces is longer than that on porous surfaces, and thehalf-life of the virus decreases with increasing temperature, whereas RH produces a stable negative inhibitory effect only in a specific humidity range. Various disinfection precautions can be implemented in daily life depending on the stability of SARS-CoV-2 on different surfaces to interrupt virus transmission, prevent COVID-19 infections, and avoid over-disinfection. Owing to the more stringent control of conditions in laboratory studies and the lack of evidence of transmission through surfaces in the real world, it is difficult to provide strong evidence for the efficiency of transmission of the contaminant from the surface to the human body. Therefore, we suggest that future research should focus on exploring the systematic study of the entire transmission process of the virus, which will provide a theoretical basis for optimizing global outbreak prevention and control measures.

Stability of SARS-CoV-2 on Inanimate Surfaces: A Review

The stability of SARS-CoV-2 for varying periods on a wide range of inanimate surfaces has raised concerns about surface transmission;however, there is still no evidence to confirm this route. In the present review, three variables affecting virus stability, namely temperature, relative humidity (RH), and initial virus titer, were considered from different experimental studies. The stability of SARS-CoV-2 on the surfaces of six different contact materials, namely plastic, metal, glass, protective equipment, paper, and fabric, and the factors affecting half-life period was systematically reviewed. The results showed that the half-life of SARS-CoV-2 on different contact materials was generally 2–10 h, up to 5 d, and as short as 30 min at 22°C, whereas the half-life of SARS-CoV-2 on non-porous surfaces was generally 5–9 h d, up to 3 d, and as short as 4 min at 22℃. The half-life on porous surfaces was generally 1–5 h, up to 2 d, and as short as 13 min at 22°C. Therefore, the half-life period of SARS-CoV-2 on non-porous surfaces is longer than that on porous surfaces, and thehalf-life of the virus decreases with increasing temperature, whereas RH produces a stable negative inhibitory effect only in a specific humidity range. Various disinfection precautions can be implemented in daily life depending on the stability of SARS-CoV-2 on different surfaces to interrupt virus transmission, prevent COVID-19 infections, and avoid over-disinfection. Owing to the more stringent control of conditions in laboratory studies and the lack of evidence of transmission through surfaces in the real world, it is difficult to provide strong evidence for the efficiency of transmission of the contaminant from the surface to the human body. Therefore, we suggest that future research should focus on exploring the systematic study of the entire transmission process of the virus, which will provide a theoretical basis for optimizing global outbreak prevention and control measures.

Potential of conserved antigenic sites in development of universal SARS-like coronavirus vaccines

Given pandemic risks of zoonotic SARS-CoV-2 variants and other SARS-like coronaviruses in the future, it is valuable to perform studies on conserved antigenic sites to design universal SARS-like coronavirus vaccines. By using antibodies obtained from convalescent COVID-19 patients, we succeeded in functional comparison of conserved antigenic sites at multiple aspects with each other, and even with SARS-CoV-2 unique antigenic sites, which promotes the cognition of process of humoral immune response to the conserved antigenic sites. The conserved antigenic sites between SARS-CoV-2 and SARS-CoV can effectively induce affinity maturation of cross-binding antibodies, finally resulting in broadly neutralizing antibodies against multiple variants of concern, which provides an important basis for universal vaccine design, however they are subdominant, putatively due to their lower accessibility relative to SARS-CoV-2 unique antigenic sites. Furthermore, we preliminarily design RBDs to improve the immunogenicity of these conserved antigenic sites. Our study focusing on conserved antigenic sites provides insights for promoting the development of universal SARS-like coronavirus vaccines, thereby enhancing our pandemic preparedness.

The neutralizing breadth of antibodies targeting diverse conserved epitopes between SARS-CoV and SARS-CoV-2.

Antibody therapeutics for the treatment of COVID-19 have been highly successful. However, the recent emergence of the Omicron variant has posed a challenge, as it evades detection by most existing SARS-CoV-2 neutralizing antibodies (nAbs). Here, we successfully generated a panel of SARS-CoV-2/SARS-CoV cross-neutralizing antibodies by sequential immunization of the two pseudoviruses. Of the potential candidates, we found that nAbs X01, X10, and X17 offer broad neutralizing potential against most variants of concern, with X17 further identified as a Class 5 nAb with undiminished neutralization against the Omicron variant. Cryo-electron microscopy structures of the three antibodies together in complex with each of the spike proteins of the prototypical SARS-CoV, SARS-CoV-2, and Delta and Omicron variants of SARS-CoV-2 defined three nonoverlapping conserved epitopes on the receptor-binding domain. The triple-antibody mixture exhibited enhanced resistance to viral evasion and effective protection against infection of the Beta variant in hamsters. Our findings will aid the development of antibody therapeutics and broad vaccines against SARS-CoV-2 and its emerging variants.

Potential of antibody pair targeting conserved antigenic sites in diagnosis of SARS-CoV-2 variants infection.

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 has become disaster for human society. As the pandemic becomes more regular, we should develop more rapid and accurate detection methods to achieve early diagnosis and treatment. Antigen detection methods based on spike protein has great potential, however, it has not been effectively developed, probably due to the torturing conformational complexity. By utilizing cross-blocking data, we clustered SARS-CoV-2 receptor binding domain (RBD)-specific monoclonal antibodies (mAbs) into 6 clusters. Subsequently, the antigenic sites for representative mAbs were identified by RBDs with designed residue substitutions. The sensitivity and specificity of selected antibody pairs was demonstrated using serial diluted samples of SARS-CoV-2 S protein and SARS-CoV S protein. Furthermore, pseudovirus system was constructed to determine the detection capability against SARS-CoV-2 and SARS-CoV. 6 RBD-specific mAbs, recognizing different antigenic sites, were identified as potential candidates for optimal antibody pairs for detection of SARS-CoV-2 S protein. By considering relative spatial position, accessibility and conservation of corresponding antigenic sites, affinity and the presence of competitive antibodies in clinical samples, 6H7-6G3 was rationally identified as optimal antibody pair for detection of both SARS-CoV-2 and SARS-CoV. Furthermore, our results showed that 6H7 and 6G3 effectively bind to SARS-CoV-2 variants of concern (VOCs). Taken together, we identified 6H7-6G3 antibody pair as a promising rapid antigen diagnostic tool in containing COVID-19 pandemic caused by multiple VOCs. Moreover, our results also provide an important reference in screening of antibody pairs detecting antigens with complex conformation.

Three SARS-CoV-2 antibodies provide broad and synergistic neutralization against variants of concern, including Omicron.

The rapidly spreading Omicron variant is highly resistant to vaccines, convalescent sera, and neutralizing antibodies (nAbs), highlighting the urgent need for potent therapeutic nAbs. Here, a panel of human nAbs from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) convalescent patients show diverse neutralization against Omicron, of which XMA01 and XMA04 maintain nanomolar affinities and excellent neutralization (half maximal inhibitory concentration [IC50]: ∼20 ng/mL). nAb XMA09 shows weak but unattenuated neutralization against all variants of concern (VOCs) as well as SARS-CoV. Structural analysis reveals that the above three antibodies could synergistically bind to the receptor-binding domains (RBDs) of both wild-type and Omicron spikes and defines the critical determinants for nAb-mediated broad neutralizations. Three nAbs confer synergistic neutralization against Omicron, resulting from the inter-antibody interaction between XMA04 and XMA01(or XMA09). Furthermore, the XMA01/XMA04 cocktail provides synergistic protection against Beta and Omicron variant infections in hamsters. In summary, our results provide insights for the rational design of antibody cocktail therapeutics or universal vaccines against Omicron.

Jointly Attention Network for Crowd Counting

Nowadays, crowd counting has shown great practical value in public safety and related fields. Most leading algorithms exploit CNN to generate density maps and have improved the estimation accuracy. However, the counting models still suffer from the challenge of huge scale variations. In order to mitigate this issue, we propose a novel approach named Jointly Attention Network (JANet) for Crowd Counting. It is composed of two major schemes: the Multi-order Scale Attention (MSA) module and the Multi-pooling Relational Channel Attention (MRCA) module. The MSA module explores meaningful high-order statistics and helps the backbone network obtain more discriminative features with rich scale information in an explicit manner. The MRCA module compactly represents the global scope relations and accounts the interdependence among all channel-wise nodes, which is complementary to MSA module. Meanwhile, the Distributed Combinatorial Loss (DCL) is designed to achieve the distributed supervision on intermediate layers at each level. Finally, we conduct extensive studies on multiple crowd counting datasets, the ShanghaiTech, the UCF-QNRF, the JHU-CROWD++, the NWPU-Crowd. The experimental results indicate that our proposed method has achieved superior performance.